Image display apparatus and in-vehicle image display apparatus

Abstract

An image display apparatus has one display screen configured to display images corresponding to a plurality of observers. The image display apparatus includes illumination unit for emitting a first light flux and a second light flux in at least two different directions in a time sharing manner, and a transmissive display element configured to display in a time sharing manner a first image using the first light flux as illumination light and a second image using the second light flux as illumination light. The illumination unit includes a first light source which emits the first light flux, a second light source which emits the second light flux, a first light guiding plate which projects the first light flux only in a direction to a first observer, and a second light guiding plate which projects the second light flux only in a direction to a second observer.

1. An image display apparatus having one display screen configured to display images corresponding to a plurality of observers, the apparatus comprising:
 illumination means for emitting a first light flux and a second light flux in at least two different directions in a time sharing manner; and 
 a transmissive display element configured to display in a time sharing manner a first image using the first light flux emitted from the illumination means as illumination light and a second image using the second light flux as illumination light, 
 wherein the illumination means includes:
 a first light source which emits the first light flux; 
 a second light source which emits the second light flux; 
 a first light guiding plate which projects the first light flux emitted from the first light source only in a direction to a first observer; and 
 a second light guiding plate which projects the second light flux emitted from the second light source only in a direction to a second observer; 
 wherein a plurality of light emitting elements are disposed adjacently to the first light guiding plate and the second light guiding plate along a raster scan direction of the transmissive display element; and 
 wherein each of the light emitting elements is individually controlled for light emission. 
 
 
     
     
       2. The image display apparatus according to  claim 1 , wherein the first light guiding plate is disposed between the transmissive display element and the second light guiding plate, and the second light flux projected from the second light guiding plate is transmitted through the first light guiding plate. 
     
     
       3. The image display apparatus according to  claim 2 , wherein a surface of the first light guiding plate facing the transmissive display element and a surface thereof facing the second light guiding plate are provided with optically flat parts for the second light flux projected from the second light guiding plate and transmitted through the first light guiding plate. 
     
     
       4. The image display apparatus according to  claim 1 , wherein a rear surface of the first light guiding plate is provided with:
 a plurality of flat surface portions which totally internally reflect incident light from the first light source to convey the incident light to an end face of the first light guiding plate opposite to the first light source; and 
 a plurality of slope portions which totally internally reflect the incident light from the first light source so that conditions of the total internal reflection in a front surface of the first light guiding plate are not satisfied and which project the incident light in the direction to the first observer. 
 
     
     
       5. The image display apparatus according to  claim 1 , wherein a front surface of the first light guiding plate is provided with:
 a plurality of flat surface portions which totally internally reflect incident light from the first light source to convey the incident light to an end face of the first light guiding plate opposite to the first light source; and 
 a plurality of exit surfaces which transmit the incident light from the first light source so that the incident light exits in the direction to the first observer. 
 
     
     
       6. The image display apparatus according to  claim 4 , wherein an angle θ between the slope portion and the flat surface portion satisfies a condition:
     n ·cos 2θ<1(θ<45 degrees) 
 where n is the refractive index of the first light guiding plate. 
 
     
     
       7. The image display apparatus according to  claim 5 , wherein the front surface of the first light guiding plate is provided with a plurality of rectangular grooves. 
     
     
       8. The image display apparatus according to  claim 7 , wherein the depth of the rectangular grooves increases as the distance increases from the first light source. 
     
     
       9. The image display apparatus according to  claim 1 , wherein the second light guiding plate has a shape different from that of the first light guiding plate or has a surface shape with a periodic structure different from that of the first light guiding plate. 
     
     
       10. The image display apparatus according to  claim 1 , wherein the second light guiding plate has the same shape as that of the first light guiding plate, and the first light guiding plate and the second light guiding plate are disposed so that they are horizontally reverse to each other. 
     
     
       11. The image display apparatus according to  claim 10 , wherein the first light source and the second light source are disposed at end face positions horizontally different when viewed from a side of the observers. 
     
     
       12. The image display apparatus according to  claim 1 , wherein the first light source and the second light source periodically generate light at different times, and the frequency of the light generated by each of the light sources is 24 Hz or more. 
     
     
       13. The image display apparatus according to  claim 1 , wherein a light absorbing member is disposed at a rear of the second light guiding plate. 
     
     
       14. The image display apparatus according to  claim 1 , wherein each of the light emitting elements periodically emits light synchronously with a raster scan by the transmissive display element. 
     
     
       15. The image display apparatus according to  claim 1 , wherein the first light guiding plate and the second light guiding plate are divided into a plurality of light guiding portions to correspond to the plurality of light emitting elements. 
     
     
       16. An in-vehicle image display apparatus which is installed in a vehicle and which has one display screen configured to display images corresponding to a plurality of observers, the apparatus comprising:
 illumination means for emitting a first light flux and a second light flux in at least two different directions in a time sharing manner; and 
 a transmissive display element configured to display in a time sharing manner a first image using the first light flux emitted from the illumination means as illumination light and a second image using the second light flux as illumination light, 
 wherein the illumination means includes:
 a first light source which emits the first light flux; 
 a second light source which emits the second light flux; 
 a first light guiding plate which projects the first light flux emitted from the first light source only in a direction to an observer on a side of a driver's seat; and 
 a second light guiding plate which projects the second light flux emitted from the second light source only in a direction to an observer on a side of a passenger seat; 
 wherein a plurality of light emitting elements are disposed adjacently to the first light guiding plate and the second light guiding plate along a raster scan direction of the transmissive display element; and 
 wherein each of the light emitting elements is individually controlled for light emission.